This project is designed to examine the three phases of iron transport by intestinal mucosa using a isolated duodenal mucosal cell model. The initial uptake of iron from the intestinal lumen is being examined by use of suspensions of isolated mucosal cells. The intracellular transport and storage of iron is being examined by the use of immunoradiometric assays for intracellular iron transport and storage proteins within mucosal cells and correlation of thse measurements with iron absorption. Release of iron to circulating transferrin is being examined by direct measurement of iron release from isolated mucosal cells and by evaluation of transferrin receptor sites on such cells. These studies are designed to improve understanding of the mechanisms and regulation of mucosal iron transport in the rat.